1. Field of the Invention
This invention relates to a novel thermoplastic resin composition which is remarkably improved in thermal stability, impact strength, hue and moldability or machinability, and more particularly to a novel heat resistant resin composition comprising an iminated copolymer prepared by iminating a copolymer obtained by copolymerizing an aromatic vinyl monomer, maleic acid anhydride and a vinyl monomer copolymerizable with the aromatic vinyl monomer and maleic acid anhydride with the use of ammonia and/or a primary amine, and mixed with a graft polymer with or without a styrene base polymer.
2. Prior Art
A process for the preparation of a copolymer comprising an aromatic vinyl monomer, maleic acid anhydride and another vinyl monomer has hitherto been known (for example, by U.S. Pat. Nos. 2,439,227, 2,914,505, 3,919,354 and 4,223,096).
A composition made of said copolymer and mixed with a graft polymer to be improved in impact strength has been also known (for example, by U.S. Pat. No. 4,197,376).
These known copolymers prepared by copolymerizing maleic acid anhydride have high thermal deformation temperatures. However, these known copolymer compositions have disadvantages that they are apt to be decomposed due to chemical reactions not only by the presence of water at high temperature but also by the action of heat since acid anhydride residues originated from maleic acid anhydride are present in the chains of the copolymers to suffer considerable limitation at the subsequent injection or extrusion molding step, and that the mechanical properties, particularly impact strength, is deteriorated accompanied with change in hue when the molded articles are allowed to contact with water or steam or exposed to high temperature.
A composition composed of an iminated copolymer prepared by iminating with alkyl amine a copolymer of an aromatic vinyl monomer and maleic acid anhydride, and a graft polymer has been known. (Reference should be made to U.S. Pat. Nos. 3,642,949 and 3,801,549). However, this known composition has a disadvantage that the impact strength thereof is not satisfactory. Also, there has been known in the art a composition composed of a graft polymer and a copolymer prepared from an aromatic vinyl monomer, acrylonitrile and an N-substituted maleimide. (Reference should be made to U.S. Pat. No. 3,652,726.) However, N-substituted maleimides are very expensive to cause economical problems, and has a disadvantage that it forms a homopolymer singly by itself leading to deterioration in impact strength and hue of the formed product.